It is known in the metallurgical testing art to employ dual alloy specimens for testing purposes. Such prior art specimens provide tensile stress, generally in a single alloy component only. For example, when the dual alloy comprises a austenitic material and a ferritic material, bonded side-by-side in some manner, as by welding or the like adjacent each other, this composite material, when subjected to the desired high temperature, will cause a parallel bending, such that the higher temperature coefficient material, namely the austenitic material, will experience only compressive stress, while the ferritic material will experience only tensile stress.
In accordance with such testing, the heat application is accomplished on a cyclic basis, and after a predetermined, desired number of heating cycles of the desired duration, the specimens are subjected to microscopic examination of the stressed surface areas, for damage.
Such testing is done in particular, in testing materials for thermal power plants, to determine likely damage at given life conditions, to use as a guide in replacement and repair of various boiler components or the like. This is because, upon repeatedly being subjected to high temperature conditions, cracks can form and gradually grow until failure occurs. The testing can be for making determinations of weld joints, or of making determinations of stress/strain of the base material structures themselves, whether they are steam pipes, pressure plates, valve components, or various other structures.